Operation method for automatic ice maker

ABSTRACT

Disclosed is an automatic ice maker which surely removes ice cubes from an ice-making unit and improves an ice-making efficiency. When the automatic ice maker starts a deicing operation, a hot gas is supplied to an evaporator and deicing water is supplied to the ice-making unit from a deicing water sprinkler to turn the frozen state at the frozen surfaces between the ice-making unit and ice cubes to a liquefaction state. When the deicing operation makes some progression and a temperature detecting unit detects that the temperature of the evaporator has reached a set temperature, a circulation pump is driven after elapse of the first set temperature to supply ice-making water to the ice-making unit from an ice-making sprinkler, promoting further separation of the ice cubes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an operation method for an automaticice maker.

2. Description of the Related Art

An automatic ice maker that automatically makes a lot of ice cubes hasan ice-making unit provided with an evaporator which sticks out of arefrigeration apparatus having a compressor, a condenser and the like.The automatic ice maker produces ice cubes by supplying ice-making waterto the ice-making unit forcibly cooled by a refrigerant circulating inthe evaporator, and separates and collects the produced ice cubes fromthe ice-making unit. The automatic ice maker has an ice-making watertank provided below the ice-making unit to store a needed amount ofice-making water. The ice-making water is supplied to the ice makingsurface of the ice-making unit by pumping the ice-making water in theice-making water tank by a circulation pump at the time of performing anice-making operation. The ice-making water which has not been frozen inthe ice-making unit is supplied to the ice-making unit again after beingcollected in the ice-making water tank.

When the ice-making operation continues and a predetermined timeelapses, the automatic ice maker determines that ice making iscompleted, and shifts the operation to a deicing operation from theice-making operation. In the deicing operation, a hot gas (hightemperature, high pressure vaporized refrigerant) pumped out from thecompressor is supplied to the evaporator by switching a hot gas valve inthe refrigeration apparatus. Accordingly, tap water is supplied to thebottom sides of the ice-making plates as deicing water to causeliquefaction at the frozen surfaces between the ice cubes and theice-making unit, thereby removing the ice cubes from the ice-making unit(see, for example, Japanese Patent Laid-Open Publication No. H5-45031).

There is a flow-down type ice maker as an automatic ice maker (see, forexample, Japanese Patent Laid-Open Publication No. H10-170113). Thisflow-down type ice maker likewise causes liquefaction at the frozensurfaces between ice cubes and ice-making plates to remove the ice cubestherefrom by supplying a hot gas from the compressor and supplying waterof normal temperature to the bottom sides of the ice-making plates.

A deicing detecting thermometer disposed at the outlet side of theevaporator detects a rise in the temperature of the hot gas circulatingin the evaporator when ice cubes are removed from the ice-making platesin the deicing operation. When the deicing detecting thermometer detectsa deicing completion temperature, the flow-down type ice makerterminates the deicing operation by stopping supplying the hot gas andthe deicing water.

FIG. 13 is a timing chart illustrating ice-making and deicing operationcycles of a conventional flow-down type ice maker. In ice-makingoperation mode, a refrigerant is supplied to the evaporator (ON) andice-making water is supplied to the ice making surfaces of theice-making plates (ON). When ice making is completed, supply of therefrigerant and the ice-making water is stopped (OFF) to terminate theice-making operation, and a hot gas and deicing water are supplied (ON)to start a deicing operation. Further, when the deicing detectingthermometer detects completion of deicing and the deicing operation isterminated and is shifted to the ice-making operation again, supply ofthe hot gas and the deicing water is stopped (OFF) and supply of therefrigerant and the ice-making water is started again. That is, asindicated by the broken-line part in FIG. 13, the flow-down type icemaker stops the hot gas and the deicing water and supplies therefrigerant and the ice-making water at the same time, when theoperation is shifted to the ice-making operation from the deicingoperation.

Such an automatic ice maker may shift the operation to the ice-makingoperation without removing all ice cubes in the deicing operation. Inthis case, new ice cubes are produced on ice cubes remaining at theice-making unit, undesirably forming deformed ice cubes called “doubleice cubes”. Further, the ice-making unit may be frozen by supercooling.As a solution to this problem, the set time of a timer (deicingcompletion detecting unit) which determines the completion of deicing ofice cubes from the ice-making unit is set longer so that the deicingoperation becomes long enough for ice cubes to be completely removed. Itis however pointed out that in this case, the deicing time becomeslonger, thus lowering the ice making efficiency.

While the deicing operation is shifted to the ice-making operation whenthe deicing detecting thermometer detects the deicing completiontemperature in the conventional flow-down type ice maker, thetemperature to be detected is determined empirically. According to theconventional flow-down type ice maker, therefore, there may be a casewhere ice remains on the ice making surfaces of the ice-making plateswhen the deicing detecting thermometer detects the deicing completiontemperature, so that ice cubes are not removed from the ice-makingplates completely.

According to the conventional flow-down type ice maker, as mentionedabove, the ice-making water and the refrigerant are supplied at the sametime as the supply of the hot gas and the deicing water is stopped. Whenthe deicing operation is terminated and is shifted to the ice-makingoperation with some ice cubes remaining on the ice-making plates, icecubes are produced with the remaining ice cubes as cores (formation ofdouble ice).

If the deicing completion temperature is set high, it is possible toachieve complete deicing. In this case, however, it is pointed out thatthe time needed for the deicing operation becomes longer, lowering theice making performance per day becomes and thus increasing the amount ofdeicing water consumed.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to overcome the inherentproblem of the conventional operation method for an automatic ice maker,and provide an operation method for an automatic ice maker capable ofsurely removing ice cubes from an ice-making unit to prevent double ice,and shortening the deicing time to improve the ice making efficiency.

To achieve the object, an operation method for an automatic ice makeraccording to the first aspect of the present invention comprises thesteps of:

in an ice-making operation, cooling an ice-making unit by supplying arefrigerant to an evaporator of the ice-making unit and generating icecubes by supplying ice-making water to the ice-making unit via acirculation pump;

in a deicing operation, supplying a hot gas to the evaporator andsupplying deicing water to the ice-making unit from a deicing watersupply unit to remove the ice cubes from the ice-making unit; and

driving the circulation pump to start supplying the ice-making water tothe ice-making unit when a first set time elapses after a temperaturedetecting unit has detected a temperature of the evaporator havingreached a predetermined set temperature.

To achieve the object, an operation method for an automatic ice makeraccording to the second aspect of the present invention comprises thesteps of:

at a time of performing an ice-making operation, supplying ice-makingwater to top sides of ice-making plates by an ice-making water supplyunit and supplying a refrigerant to an evaporator disposed in azigzagged form between bottom sides of the ice-making plates;

when an operation shifts to a deicing operation upon detection ofgeneration of ice cubes on the top sides of the ice-making plates,stopping supplying the ice-making water to the top sides of theice-making plates, and supplying deicing water to the bottom sides ofthe ice-making plates after stopping supplying the refrigerant to theevaporator to thereby promote melt separation of the ice cubes from theice-making plates; and

causing a controller to control the ice-making water supply unit in sucha way as to supply the ice-making water to the top sides of theice-making plates before terminating the deicing operation so that icecubes remaining on the top sides of the ice-making plates are removed bythe ice-making water.

According to the operation method for an automatic ice maker accordingto the first aspect of invention, the circulation pump is driven tostart supplying the ice-making water to the ice-making unit in thedeicing operation when the first set time elapses after the temperaturedetecting unit has detected the temperature of the evaporator havingreached the predetermined set temperature. Because this can shorten thedeicing time, it is possible to decrease the amount of deicing waterneeded can be reduced and increase the ice making efficiency.

According to the operation method, supply of the deicing water from thedeicing water supply unit is stopped by driving the circulation pump,making it possible to make the amount of deicing water smaller.

According to the operation method, supply of the deicing water from thedeicing water supply unit is stopped when a second set time set shorterthan the first set time elapses after a temperature detecting unit hasdetected a temperature of the evaporator having reached thepredetermined set temperature, making it possible to further reduce theamount of deicing water.

According to the operation method of the second aspect of invention,ice-making water is supplied to the top sides of the ice-making platesbefore the deicing operation is terminated, so that ice cubes remainingon the top sides are surely separated by the ice-making water, thuspreventing double ice making. This makes it possible to producehigh-quality ice cubes of uniform shape and shorten the deicing time.

In the second aspect of the invention, the controller controls theice-making water supply unit to start supplying the ice-making waterwhen an ice-making-water supply start detecting unit detects a presetice-making-water supply start condition before a deicing completiondetecting unit which detects completion of the deicing operation detectscompletion of deicing. Accordingly, liquefaction of ice cubes byice-making water is suppressed as compared with a case of continuoussupply of ice-making water, so that supply of the ice-making water canbe carried out at a relatively early stage of the deicing operation.This operation method makes the deicing efficiency higher than that ofthe case of continuously supplying ice-making water in deicing operationmode, so that the deicing time can be made shorter, thus resulting in animproved ice making performance.

In the second aspect of the invention or the previously describedmodification thereof, in a case of supplying the ice-making water to thetop sides of the ice-making plates before terminating the deicingoperation, the controller controls the ice-making water supply unit tointermittently supply the ice-making water. This operation method canreduce the amount of ice-making water to be sprayed into the ice tank byintermittently supplying the ice-making water in deicing operation mode.

In any one of the second aspect of the invention and the previouslydescribed two modifications thereof, when supply of the ice-making waterto the top sides of the ice-making plates is started before terminatingthe deicing operation, the controller controls the deicing water supplyunit which supplies the deicing water ice-making water supply unit,thereby stopping supplying the deicing water to the bottom sides of theice-making plates. This operation method can make the amount ofice-deicing water to be used in the deicing operation smaller than thatconventionally needed by stopping supplying the deicing water to thebottom sides of the ice-making plates when supply of the ice-makingwater to the top sides of the ice-making plates is started before thedeicing operation ends.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing an automatic ice maker accordingto a preferable first embodiment of the present invention;

FIG. 2 is a control block diagram of the automatic ice maker of thefirst embodiment;

FIG. 3 is a flowchart illustrating the first half of the procedures ofthe deicing operation of the automatic ice maker of the firstembodiment;

FIG. 4 is a flowchart illustrating the second half of the procedures ofthe deicing operation of the automatic ice maker of the firstembodiment;

FIG. 5 is a flowchart illustrating the second half of the procedures ofthe deicing operation of the automatic ice maker according to a secondembodiment;

FIG. 6 is a control block diagram of an automatic ice maker according toa third embodiment;

FIG. 7 is a flowchart illustrating the second half of the procedures ofthe deicing operation of the automatic ice maker of the thirdembodiment;

FIG. 8 is a schematic structural diagram showing a flow-down type icemaker according to a fourth embodiment;

FIG. 9 is a flowchart illustrating an operation method for the flow-downtype ice maker of the fourth embodiment;

FIG. 10 is a timing chart illustrating the operation cycle of theflow-down type ice maker of the fourth embodiment;

FIG. 11 is a flowchart illustrating an operation method for a flow-downtype ice maker according to a fifth embodiment;

FIG. 12 is a timing chart illustrating the operation cycle of theflow-down type ice maker of the fifth embodiment; and

FIG. 13 is a timing chart illustrating the operation cycle of theconventional flow-down type ice maker.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Operation methods for an automatic ice maker according to preferredembodiments of the present invention will be described below referringto the accompanying drawings.

First Embodiment

FIG. 1 shows the schematic configuration of a flow-down type automaticice maker as an automatic ice maker according to a first embodiment. Theautomatic ice maker has an evaporator 14 closely fixed to the backsideof an ice-making unit 10 disposed approximately vertically in anice-making room. The evaporator 14 is a tubular member sticking out froma refrigeration apparatus 30 to be described later and extending in azigzagged form in the horizontal direction of the ice-making unit 10.The evaporator 14 forcibly cools down the ice-making unit 10 with arefrigerant supplied to the evaporator 14 in ice-making operation mode.

An ice-making water tank 20 which retains a predetermined amount ofice-making water is provided under the ice-making unit 10. In performingan ice-making operation, ice-making water is supplied to the ice makingsurface of the ice-making unit 10 via a circulation pump PM from theice-making water tank 20 in the automatic ice maker. A guide plate 18 isdisposed inclined directly below the ice-making unit 10. The guide plate18 guides ice cubes M, which are separated from the ice-making unit 10in a deicing operation, to a stocker 16 located below. The guide plate18 has multiple through holes (not shown) bored therein. In theice-making operation, the ice-making water supplied to the ice makingsurface of the ice-making unit 10 is collected into the ice-making watertank 20 through the through holes of the guide plate 18.

An ice-making sprinkler 24 is disposed above the ice-making unit 10. Theice-making sprinkler 24 is connected to an ice-making water supply pipe22 extending out from the ice-making water tank 20 via the circulationpump PM. The ice-making sprinkler 24 has multiple spray holes (notshown) formed therein. In ice-making operation mode, the ice-makingsprinkler 24 sprays ice-making water, pumped out from the ice-makingwater tank 20, to the ice making surface of the ice-making unit 10cooled to the freezing temperature through the spray holes. As a result,ice cubes M are produced on the ice making surface of the ice-makingunit 10.

A deicing water sprinkler (deicing water supply unit) 28 havingunillustrated perforations is disposed above the ice-making unit 10. Tapwater is supplied to the deicing water sprinkler 28 via a water supplypipe 26 connected to an external water source. A water supply valve(deicing water supply unit) WV is disposed in the water supply pipe 26to be able to close the path of the water supply pipe 26 in anopenable/closable manner. With the water supply valve WV opened in thedeicing operation, deicing water is supplied to the deicing watersprinkler 28. At this time, as the deicing water is sprayed onto thebottom side of the ice-making unit 10 from the above-mentionedperforations, the temperature of the ice-making unit 10 cooled in theice-making operation is increased by the deicing water. The deicingwater is collected into the ice-making water tank 20 to be used asice-making water in a next ice-making operation. An excess amount of thedeicing water flown down to the ice-making water tank 20 that exceedsthe pondage is discharged from an overflow pipe 21.

The evaporator 14 is provided with a temperature detecting unit TH whichdetects that the temperature of the evaporator 14 has reached apredetermined set temperature T1 since the initiation of the deicingoperation. After a first set time which is before completion of thedeicing operation elapses, the circulation pump PM is driven. As aresult, the ice-making water is supplied to the ice-making unit 10 fromthe ice-making sprinkler 24, further promoting separation of ice cubesM.

The refrigeration apparatus 30 basically includes a compressor CM, acondenser CD, an expansion unit EV and the evaporator 14 provided at thebottom side of the ice-making unit 10 (see FIG. 1). The compressor CM,the condenser CD and the expansion unit EV are disposed in a mechanicalchamber (not shown). The individual components of the refrigerationapparatus 30 are connected together by a refrigerant pipe 34, and therefrigerant circulates in the order of the compressor CM, the condenserCD and the expansion unit EV. That is, the vaporized refrigerantcompressed by the compressor CM is condensed in the condenser CD to beliquefied. Thereafter, the liquefied refrigerant is depressurized by theexpansion unit EV and flows into the evaporator 14. The liquefiedrefrigerant is expanded and vaporized by the evaporator 14, andexchanges heat with the ice-making unit 10 to forcibly cool theice-making unit 10 down to the degree of frost. The vaporizedrefrigerant that has exchanged heat with the evaporator 14 is fed backto the compressor CM.

The refrigeration apparatus 30 has a bypass pipe 36 through which a hotgas can be supplied directly to the evaporator 14 from the compressor CMwithout going through the condenser CD and the expansion unit EV.Disposed in the bypass pipe 36 is a hot gas valve HV which closes thepath of the bypass pipe 36 in an openable/closable manner. With the hotgas valve HV opened in the deicing operation, the temperature of theice-making unit 10 is increased by the hot gas supplied to theevaporator 14. Reference numeral “FM” in FIG. 1 denotes a fan motorwhich is driven during the ice-making operation to cool down thecondenser CD.

As shown in FIG. 2, the individual components constituting therefrigeration apparatus 30, such as the compressor CM, the fan motor FMand the hot gas valve HV, the circulation pump PM and the water supplyvalve WV are controlled by a controller C. The controller C has a timerTM and various counters, such as a water supply counter WI, a watersupply end counter WF, a circulation pump counter PS, a deicing counterFD and a backup counter BU, which count by a predetermined value (“1” inthe first embodiment) in response to the action of the timer TM. Thewater supply counter WI manages the water supply state in the deicingoperation. The water supply end counter WF manages the timing forcompleting water supply and closes the water supply valve WV in thedeicing operation. The circulation pump counter PS manages the timingfor driving the circulation pump PM in the deicing operation. Thedeicing counter FD manages the timing for completing the deicingoperation and serves as a deicing completion detecting unit which closesthe water supply valve WV and the hot gas valve HV. The backup counterBU closes the water supply valve WV and the hot gas valve HV inemergency to avoid an abnormal deicing operation.

The controller C executes a “timer interruption program” by interruptionevery time the timer TM measures a predetermined time. Accordingly, awater supply count value WICT of the water supply counter WI and abackup count value BUCT of the backup counter BU are counted up by “1”.Likewise, a water-supply completion count value WFCT of the water supplyend counter WF, a deicing count value FDCT of the deicing counter FD anda circulation pump count value PSCT of the circulation pump counter PSare counted up by “1”. When the count value of each counter reaches aset value previously set, each corresponding component performs apredetermined operation.

The temperature detecting unit TH is disposed in the refrigerant pipe 34connected to the outlet side of the evaporator 14 (see FIG. 1).Detecting the temperature of the refrigerant flowing in the refrigerantpipe 34, the temperature detecting unit TH monitors the temperature ofthe evaporator 14 and determines the liquefaction state of ice cubes Min the deicing operation. The result of temperature detection by thetemperature detecting unit TH is input to the controller C. When thetemperature detection result is equal to or greater than the settemperature T1, the deicing counter FD and the circulation pump counterPS start counting. The circulation pump PM is driven after the first settime elapses after detection of the set temperature T1 by thetemperature detecting unit TH, and ice-making water is sprayed to theice-making unit 10. The first set time is the time at which thecirculation pump count value PSCT has reached a set value CT101. Whenthe deicing count value FDCT reaches a set value CT4 thereafter, thewater supply valve WV and the hot gas valve HV are closed, stopping thedeicing operation. The set temperature T1 is set to a temperature (e.g.,9° C. or so) just before ice cubes M on the ice making surface of theice-making unit 10 starts melting and the temperature near the outlet ofthe evaporator 14 hardly changes (is saturated). The set value CT4 ofthe deicing count value FDCT is set larger than the count value CT101 ofthe circulation pump count value PSCT.

A temperature detection flag TFLG is set in the controller C. Thetemperature detection flag TFLG is changeover means which setsconditional branching for progressing or repeating the deicing operationbased on the result of detection by the temperature detecting unit TH.

Operation of First Embodiment

An operation method for the automatic ice maker according to the firstembodiment will be described below referring to flowcharts shown inFIGS. 3 and 4. When the automatic ice maker starts the ice-makingoperation, the ice-making unit 10 exchanges heat with the refrigerantcirculating in the evaporator 14 to be forcibly cooled. The ice-makingwater is supplied to the ice making surface of the ice-making unit 10from the ice-making water tank 20 by the circulation pump PM, andgradually starts being frozen on the ice making surface. The ice-makingwater which has not being frozen is collected into the ice-making watertank 20 via the through holes of the guide plate 18, and is suppliedagain to the ice-making unit 10 by the circulation pump PM. Whencompletely producing ice cubes M on the ice making surface of theice-making unit 10, the automatic ice maker stops the ice-makingoperation and shifts to the deicing operation. At this time, thecompressor CM is kept driven, and the fan motor FM is stopped (step S1).

When the deicing operation starts, the circulation pump PM is stopped tostop supply of the ice-making water from the ice-making sprinkler 24. Asthe hot gas valve HV is opened, the hot gas is supplied to theevaporator 14 (step S2). At the same time, the water supply valve WV isopened to supply the deicing water to the bottom side of the ice-makingunit 10 from the deicing water sprinkler 28, increasing the temperatureof the ice-making unit 10 (step S2). As a result, liquefaction at thefrozen surfaces of the ice cubes M formed on the ice making surface ofthe ice-making unit 10 gradually occurs.

The backup count value BUCT of the backup counter BU, the water supplycount value WICT of the water supply counter WI and the water-supplycompletion count value WFCT of the water supply end counter WF are resetto “0”. Further, after the temperature detection flag TFLG is set to aninitial value “0” (step S3), the operation goes to step S4. Each counterWI, WF, BU counts up the corresponding count value WICT, WFCT, BUCT by“1” every time the timer TM measures a predetermined time.

In step S4, it is determined whether or not the backup count value BUCTof the backup counter BU is equal to or greater than a set value CT2.The set value CT2 is set to a value equivalent to a time (e.g., 20minutes or so) larger than the time needed for all the ice cubes M to beseparated from the ice-making unit 10 in the normal deicing operation.When the backup count value BUCT is smaller than the set value CT2, theflow goes to a decision on the water supply count value WICT of thewater supply counter WI (step S5). When the backup count value BUCT isequal to or greater than the set value CT2, on the other hand, the hotgas valve HV is closed to stop supplying the hot gas to the evaporator14 (step S13). The deicing operation takes an emergency stop as thewater supply valve WV is closed to stop supplying the deicing water tothe ice-making unit 10 from the deicing water sprinkler 28 (step S13).At this time, the controller C may generate an alarm or the like. Whenthe completion of deicing takes time and the backup count value BUCTbecomes equal to or greater than the set value CT2, it is decided thatsome kind of abnormality has occurred, and the deicing operation isstopped. This prevents wasteful consumption of the deicing water andreduces the load of the compressor CM.

Next, it is determined whether the amount of the deicing water suppliedto the bottom side of the ice-making unit 10 from the deicing watersprinkler 28 is large or small (step S5). In this step S5, the amount ofthe deicing water stored in the ice-making water tank 20 is determinedby determining whether or not the water supply count value WICT of thewater supply counter WI is equal to or greater than a set value CT6. Theset value CT6 is set to a value equivalent to the time (e.g., 3 minutesor so) needed for filling up the ice-making water tank 20 with thenecessary amount of the ice-making water in the normal deicingoperation. When the water supply count value WICT is equal to or greaterthan the set value CT6, the flow goes to a decision on the water-supplycompletion count value WFCT of the water supply end counter WF (stepS6). When the water supply count value WICT is smaller than the setvalue CT6, on the other hand, the flow returns to step S4 to repeat theprocesses of step S4 and step S5.

In step S6, it is determined whether or not the water-supply completioncount value WFCT of the water supply end counter WF is equal to orgreater than a set value CT3 previously set. When the time of thedeicing operation becomes longer due to the ambient temperature, thetemperature of the deicing water or the like in step S5, an excessamount of the deicing water is discharged from the overflow pipe 21since a certain amount of the deicing water is stored in the ice-makingwater tank 20. When the water-supply completion count value WFCT isequal to or greater than the set value CT3 in step S6, it is determinedthat the supply time of the deicing water is abnormally long, so thatthe water supply valve WV is closed to stop supplying the deicing waterfrom the deicing water sprinkler 28 (step S61). Then, the flow goes tostep S7. Accordingly, the deicing water is not excessively supplied tothe ice-making unit 10, saving the amount of the deicing water. When thewater-supply completion count value WFCT is smaller than the set valueCT3, the flow goes to step S7 with the water supply valve WV left open.The set value CT3 of the water-supply completion count value WFCT is setlarger than the set value CT6 of the water supply count value WICT,e.g., 6 minutes or so.

In step S7, the flow branches depending on the value of the temperaturedetection flag TFLG. When the value of the temperature detection flagTFLG is the initial value “0”, the flow goes to a step of detecting thetemperature of the evaporator 14 (step S8) by the temperature detectingunit TH. In step S8, when the temperature detected by the temperaturedetecting unit TH is equal to or greater than the set temperature T1,the deicing count value FDCT of the deicing counter FD and thecirculation pump count value PSCT of the circulation pump counter PS arereset to “0”. In addition, the deicing counter FD and the circulationpump counter PS start counting and the temperature detection flag TFLGis changed from “0” to “1” (step S9), after which the flow returns tostep S4.

When the temperature of the evaporator 14 has not reached the settemperature T1 yet, however, the deicing counter FD and the circulationpump counter PS are not activated. That is, the flow goes to step S4without going through step S9, and steps S4 to S8 are repeated until thetemperature detecting unit TH detects the set temperature T1. Solidlines (1), (2) and (3) in FIG. 3 connect to solid lines (1), (2) and (3)in FIG. 4, respectively.

When the temperature detecting unit TH detects the set temperature T1,the temperature detection flag TFLG is changed to “1”, shifting theprocess to step S10 from step S7, so that the deicing operation furtherprogresses. That is, it is determined that as the temperature of theevaporator 14 rises to the set temperature T1, the frozen state betweenthe ice-making unit 10 and the ice making surfaces of the ice cubes M isreleased to some extent. In step S10, the timing for spraying ice-makingwater to the ice-making unit 10 from the ice-making sprinkler 24 isdetermined. When the circulation pump count value PSCT of thecirculation pump counter PS exceeds the first set time greater than theset value CT101, the circulation pump PM is driven (step S11). As aresult, the ice-making water is pumped out from the ice-making watertank 20 and supplied to the ice-making unit 10 from the ice-makingsprinkler 24. Then, the increased temperature of the ice-making unit 10with the hot gas and the deicing water as well as the ice-making waterflowing down the ice making surface of the ice-making unit 10 furtherpromotes the separation of the ice cubes M from the ice-making unit 10.When the circulation pump count value PSCT is smaller than the set valueCT101, on the other hand, the flow returns to step S4 and the processesof steps S4 to S7 are repeated to continue the deicing operation.

When the deicing count value FDCT of the deicing counter FD reaches theset value CT4, it is determined that all the ice cubes M are separatedfrom the ice-making unit 10, and the deicing operation is completed(step S12). At this time, the water supply valve WV is closed to stopsupplying the deicing water and the hot gas valve HV is closed to stopsupplying the hot gas to the evaporator 14 (step S13), thereby stoppingincreasing the temperature of the ice-making unit 10. When the deicingcount value FDCT has not reached the set value CT4, on the other hand,the flow returns to step S4 and the processes of steps S4 to S7 and stepS10 are repeated. The set value CT4 of the deicing count value FDCT isset to a value (equivalent to one minute or so) greater than the setvalue CT101 of the circulation pump count value PSCT. That is, the setvalue CT4 is set in such a way that the ice-making water can be suppliedto the ice-making unit 10 before the deicing operation is terminated.

Then, the automatic ice maker repeats the cycle of shifting to theice-making operation again after going through a needed operation suchas the water discharge operation.

In the deicing operation, the automatic ice maker drives the circulationpump PM to supply the ice-making water to the ice making surface of theice-making unit 10 from the ice-making sprinkler 24 after thetemperature detecting unit TH detects the set temperature T1.Accordingly, liquefaction at the frozen surfaces of the ice cubes Mdirectly occurs, thus quickening the timing of separating the ice cubesM. That is, the set value CT4 of the deicing count value FDCT can be setsmall, making it possible to shorten the time to complete the deicingoperation since the detection of the set temperature T1 by thetemperature detecting unit TH. Therefore, the overall time of thedeicing operation is shortened with the ice cubes M surely separatedfrom the ice-making unit 10. This can reduce the amount of the deicingwater needed and improve the ice making efficiency.

If the automatic ice maker supplies ice-making water to the ice makingsurface of the ice-making unit 10 immediately after the transition fromthe ice-making operation to the deicing operation, the ice-making watermay be frozen. Because the ice-making water is supplied to theice-making unit 10 which is warmed to some degree in the automatic icemaker of the first embodiment, however, it is possible to prevent theice-making water from being frozen and adequately promote separation ofthe ice cubes M. In addition, as the ice-making water is supplied fromthe ice-making sprinkler 24 disposed above the ice-making unit 10,separation of the ice cubes M is promoted more adequately by the forceof the ice-making water flowing down along the ice making surface. Theremay be a case where surface tension is generated by the liquefactionbetween the ice cubes M and the ice making surface, making it difficultfor the ice cubes M to fall, during separation of the ice cubes M fromthe ice-making unit 10. Even in this case, the ice-making water whosetemperature is relatively higher than the temperature of the ice cubes Mis directly sprayed onto the ice cubes M, making it possible to reducethe surface tension and promote deicing.

The set value of each counter and the measuring time of the timer TM canbe set arbitrarily according to the environmental condition, such as theambient temperature or the temperature of the deicing water. Inparticular, because the count values of the individual counters can bechanged collectively by changing the measuring time of the timer TM, theset values can be easily changed. Because the automatic ice maker canalways perform the deicing operation under the optimal operationalcondition by adequately changing the operational condition, the icemaking efficiency can be improved.

Second Embodiment

FIG. 5 is a flowchart illustrating an operation method for an automaticice maker according to the second embodiment. Solid lines (1), (2) and(3) in FIG. 5 connect to solid lines (1), (2) and (3) in FIG. 3,respectively. The first half part of the deicing operation of the secondembodiment is similar to the first half part of the deicing operation ofthe first embodiment explained referring to FIG. 3. That is, thefundamental portion of the second embodiment is similar to that of thefirst embodiment, so that only different portions will be described.

The automatic ice maker of the second embodiment supplies ice-makingwater to the ice-making unit 10 by driving the circulation pump PM afterthe first set time elapses since detection by the temperature detectingunit TH that the temperature of the evaporator 14 has reached the settemperature T1. At the same time, the water supply valve WV is closed tostop supplying the deicing water from the deicing water sprinkler 28. Asshown in FIG. 5, when the temperature detecting unit TH detects the settemperature T1 (step S8), it may be determined that liquefaction of icecubes M is progressing to some degree. Accordingly, the deicing counter(deicing completion detecting unit) FD and the circulation pump counterPS start counting the deicing count value FDCT and the circulation pumpcount value PSCT, respectively (step S9). In step S9, the temperaturedetection flag TFLG is switched to “1”, permitting the shifting fromstep S7 to step S10.

When the circulation pump count value PSCT reaches the set value CT101,the circulation pump PM is driven to spray the ice-making water to theice making surface of the ice-making unit 10 from the ice-makingsprinkler 24 (step S10). As the water supply valve WV is closed, thedeicing water sprinkler 28 stops spraying the deicing water to theice-making unit 10 (step S11 a). When the set value CT101 is counted,the first set time is reached. When the deicing count value FDCT becomesthe set value CT4, it is determined that all the ice cubes M areseparated from the ice-making unit 10 (step S12). As a result, the hotgas valve HV is closed to stop supplying the hot gas to the evaporator14 (step S13 a), thereby stopping increasing the temperature of theice-making unit 10.

The operation method for the automatic ice maker of the secondembodiment has an operational advantage of being able to further reducethe amount of the deicing water to be used in the deicing operation ascompared with the first embodiment, in addition to the operationaladvantages of the operation method of the first embodiment. Theice-making water supplied to the ice-making unit 10 from the ice-makingwater tank 20 by the circulation pump PM circulates in the automatic icemaker. The deicing water to be supplied from an external water source isdischarged outside through the overflow pipe 21 if the amount of thedeicing water exceeds the pondage of the ice-making water tank 20. Thatis, the discharge amount of the deicing water can be reduced by stoppingthe supply of the deicing water at the time of supplying the ice-makingwater to the ice-making unit 10 by means of the circulation pump PM. Theice-making water which directly contacts the ice cubes M is excellent indeicing efficiency than the deicing water which indirectly increases thetemperature of the ice cubes M from the bottom side of the ice-makingunit 10. Therefore, reduction in the deicing efficiency caused bystopping the supply of the deicing water is avoided.

Third Embodiment

FIG. 6 is a control block diagram of an automatic ice maker according tothe third embodiment. A controller C2 of the third embodiment has awater supply valve counter WS added to the controller C described in theforegoing description of the first embodiment. The water supply valvecounter WS manages the timing for stopping supplying the deicing waterafter the temperature detecting unit TH detects the set temperature T1.FIG. 7 is a flowchart illustrating an operation method for the automaticice maker according to the third embodiment. Solid lines (1), (2) and(3) in FIG. 7 connect to solid lines (1), (2) and (3) in FIG. 3,respectively. The first half part of the deicing operation of the thirdembodiment is similar to the first half part of the deicing operation ofthe first embodiment explained referring to FIG. 3. That is, thefundamental portion of the third embodiment is similar to that of thefirst embodiment, so that only different portions will be described.

The automatic ice maker of the third embodiment supplies ice-makingwater to the ice-making unit 10 by driving the circulation pump PM afterthe first set time elapses since detection by the temperature detectingunit TH that the temperature of the evaporator 14 has reached the settemperature T1. When a second set time elapses after the detection ofthe set temperature T1 by the temperature detecting unit TH, the watersupply valve WV is closed to stop supplying the deicing water from thedeicing water sprinkler 28. The second set time is set shorter than thefirst set time so that supply of the deicing water is stopped before thecirculation pump PM is driven.

As shown in FIG. 7, when the temperature detecting unit TH detects thetemperature of the evaporator 14 having reached the set temperature T1(step S8), it is determined that liquefaction of ice cubes M isprogressing to some degree. Accordingly, the deicing counter (deicingcompletion detecting unit) FD, the circulation pump counter PS and thewater supply valve counter WS start counting the deicing count valueFDCT, the circulation pump count value PSCT and a water supply valvecount value WSCT, respectively (step S9 a). In step S9 a, thetemperature detection flag TFLG is switched to “1”, permitting theshifting of the deicing operation from step S7 (to step S102).

When the water supply valve count value WSCT of the water supply valvecounter WS reaches a set value CT102 (step S102), the water supply valveWV is closed to stop spraying the deicing water from the deicing watersprinkler 28 (step S111). Then, the automatic ice maker goes to stepS10. The set value CT102 is set to a value equivalent to the second settime.

When the circulation pump count value PSCT of the circulation pumpcounter PS reaches the set value CT101 (step S10), the circulation pumpPM is driven to spray the ice-making water to the ice making surface ofthe ice-making unit 10 from the ice-making sprinkler 24 (step S112).Then, the automatic ice maker proceeds to step S12. The set value CT101is set to a value equivalent to the first set time.

When the deicing count value FDCT becomes the set value CT4 in step S12,it is determined that all the ice cubes M are separated from theice-making unit 10. As a result, the hot gas valve HV is closed to stopsupplying the hot gas to the evaporator 14 (step S13 a), therebystopping increasing the temperature of the ice-making unit 10.

According to the operation method for the automatic ice maker of thethird embodiment, because supply of the deicing water is stopped at anearly timing after detection of the set temperature T1 by thetemperature detecting unit TH, the amount of water to be used in thedeicing operation can be reduced more than the second embodiment can.The operation method for the automatic ice maker of the third embodimentdemonstrates the operational advantages of the operation method of thefirst embodiment or the second embodiment.

Fourth Embodiment

FIG. 8 shows the schematic configuration of a flow-down type ice maker110 which executes an operation method for an automatic ice makeraccording to the fourth embodiment. An ice-making unit 111 of theflow-down type ice maker 110 has a pair of vertical ice-making plates112, 112 arranged facing each other at a predetermined distancetherebetween, and an evaporator 114 fixed between the opposing sides ofthe ice-making plates 112, 112. The evaporator 114 sticks out from therefrigeration system and extends in a zigzagged form in the horizontaldirection of the ice-making plates 112. A guide plate 120 is disposedinclined directly below each ice-making plate 112. The guide plate 120guides ice cubes M, which are separated from each ice-making plate 112in a deicing operation, to a stocker 118 located below. Each guide plate120 has a plurality of through holes 122 formed therein. In performingan ice-making operation, an unfrozen part of ice-making water 124supplied to the ice making surface (top side) 132 of the ice-makingplate 112 is collected into an underlying ice-making water tank 126 viathe through holes 122. The ice-making water tank 126 collects deicingwater 130 supplied to the bottom side, 128, of the ice-making plate 112in the deicing operation.

A double pipe 138 is disposed above the ice-making unit 111. The doublepipe 138 has an ice-making water spray pipe 134 which supplies theice-making water 124 to the ice making surface 132 of each ice-makingplate 112, and a deicing water spray pipe 136 which supplies the deicingwater 130 to the bottom side 128. The ice-making water spray pipe 134 isconnected to an ice-making water supply pipe 142 extending out from theice-making water tank 126 via a circulation pump (ice-making watersupply unit) 140 disposed in the ice maker. In ice-making operationmode, the ice-making water 124 is pumped out from the ice-making watertank 126 to each ice-making plate 112 by the circulation pump 140 and issprayed onto the ice making surface 132 cooled down to the freezingtemperature, thus forming hemispherical ice cubes M at the ice makingsurface 132. The circulation pump 140 is connected to the controller 144which switches between supply of the ice-making water 124 and stoppingsupplying the ice-making water 124 in the ice-making operation and thedeicing operation.

The deicing water spray pipe 136, provided inside the double pipe 138,sprays water of normal temperature (deicing water 130) to the bottomsides 128, 128 of both ice-making plates 112, 112 in deicing operationmode. The deicing water spray pipe 136 is connected to a deicing watersupply pipe 148 connected to an external water source (not shown). Awater supply valve (deicing water supply unit) 146 is disposed in thedeicing water supply pipe 148. That is, in the deicing operation, a hotgas circulating in the evaporator 114 heats each ice-making plate 112whose bottom side 128 is sprayed with the deicing water 130 from thedeicing water spray pipe 136. As a result, liquefaction at the frozensurfaces between each ice making surface 132 and the ice cubes M occurs.The water supply valve 146 is connected to the controller 144 whichswitches between supply of the deicing water 130 and stopping supplyingthe deicing water 130 in the deicing operation.

A deicing thermometer 152 is tightly disposed at the outlet side of theevaporator 114. The deicing thermometer 152 is connected to thecontroller 144, and serves as the deicing completion detecting unit thatdetects the temperature of the hot gas circulating in the evaporator114. When the deicing thermometer 152 detects that the temperature ofthe hot gas has reached a preset deicing completion temperature in thedeicing operation, the controller 144 terminates the deicing operationand shifts to the ice-making operation. Note that the temperature of thehot gas rapidly increases when the ice cubes M are separated from eachice-making plate 112.

When the deicing thermometer 152 detects an ice-making water supplytemperature (ice-making-water supply start condition) in the deicingoperation, the controller 144 controls the circulation pump 140 tosupply the ice-making water 124 to the ice making surface 132 from theice-making water spray pipe 134. The ice-making water supply temperatureis set to a temperature, for example, lower than the deicing completiontemperature by about 10° C. to 20° C. That is, as the ice-making water124 is supplied to the ice making surface 132 before deicing completes,the separation of the ice cubes M remaining on the ice making surface132 is promoted. The deicing completion temperature and the ice-makingwater supply temperature have only to be set to adequate valuesaccording to the ice-making performance of the flow-down type ice maker110, the site thereof, and the like. It is to be noted that if theice-making water supply temperature is set considerably lower than thedeicing completion temperature, the ice-making water 124 is suppliedwithout liquefaction taking place between the ice cubes M and theice-making plate 112. In this case, because the supply amount of theice-making water 124 needed in completing deicing is increased, it ispreferable that the ice-making water supply temperature should be setlower than the deicing completion temperature by 10° C. or so. In thefourth embodiment, the deicing thermometer 152 serves as theice-making-water supply start detecting unit.

The refrigeration apparatus of the flow-down type ice maker 110 isbasically the same as the conventional ice maker. In the refrigerationapparatus, the vaporized refrigerant compressed by a compressor 154passes through a discharge pipe 168 to a condenser 156 where therefrigerant is liquefied. The liquefied refrigerant is dehumidified by adryer 158 and is then depressurized by a capillary tube 160. Theliquefied refrigerant flows into the evaporator 114 and is expanded andevaporated at a burst, exchanging heat with each ice-making plate 112 tothereby cool the ice-making plate 112 down to the degree of frost. Thevaporized refrigerant vaporized in the evaporator 114 and the liquefiedrefrigerant unvaporized flow into an accumulator 162 in a gas-vaporphase, and is separated into a gas and a liquid therein. The vaporizedrefrigerant is fed back to the compressor 154 via a suction pipe 164,and the liquid-phase refrigerant is stored in the accumulator 162.

A hot gas pipe 166 is branched from the discharge pipe 168 of thecompressor 154 in the refrigeration apparatus, and communicates with theinlet side of the evaporator 114 via the hot gas valve HV. The hot gasvalve HV is controlled by the controller 144 in such a way as to beopened only during the deicing operation and closed in the ice-makingoperation. In performing the deicing operation, the hot gas expelledfrom the compressor 154 flows into the evaporator 114 via the hot gaspipe 166 and exchanges heat with each ice-making plate 112. The hot gasflowing out from the evaporator 114 flows into the accumulator 162,vaporizes the liquefied refrigerant remaining in the accumulator 162 toyield a liquefied refrigerant. Accordingly, the liquefied refrigerant isfed back again to the compressor 154 from the suction pipe 164.

Operation of Fourth Embodiment

An operation method for the flow-down type ice maker 110 of the fourthembodiment will be described below. As shown in FIG. 9, when ice makingis completed, the controller 144 stops the circulation pump 140 to stopsupplying the ice-making water 124 from the ice-making water spray pipe134. In addition, the controller 144 opens the hot gas valve HV to stopsupplying the refrigerant to the evaporator 114, and then terminates theice-making operation (S201).

The controller 144 opens the water supply valve 146 to supply thedeicing water 124 to the bottom side 128 of each ice-making plate 112from the deicing water spray pipe 136. Further, opening the hot gasvalve HV supplies the hot gas to the evaporator 114, starting thedeicing operation (S202). As shown in FIG. 10, at the time of switchingfrom the ice-making operation to the deicing operation, the supply ofthe refrigerant and the ice-making water 124 is stopped (OFF), and, atthe same time, the supply of the hot gas and the deicing water isstarted (ON). The start of the deicing operation causes liquefaction tostart taking place at the frozen surfaces of the ice cubes M frozen onthe ice making surface 132 due to the hot gas and the deicing water 130supplied.

In the deicing operation, as liquefaction at the frozen surfaces betweenthe ice cubes M and the ice making surface 132 progresses, thetemperature of the hot gas on the outlet side of the evaporator 114gradually rises. When a predetermined time elapses since the start ofthe deicing operation and deicing approaches its completion, the deicingthermometer 152 detects the ice-making water supply temperature (S203).At this time, liquefaction at the frozen surfaces of the ice cubes M hasmade some progress, and some of the ice cubes M are separated from theice-making plate 112 due to their own weight, or some are remainingthereon without being liquefied. When the deicing thermometer 152detects the ice-making water supply temperature, the controller 144activates the circulation pump 140 to pump out the ice-making water 124to the ice-making water spray pipe 134 and starts supplying theice-making water 124 to the ice making surface 132 (ON). Further, thecontroller 144 closes the water supply valve 146 to stop supplying thedeicing water 130 from the deicing water spray pipe 136 (OFF) (S204).

That is, the liquefaction at the frozen surfaces between the ice cubes Mand the ice-making plate 112 is accelerated by the ice-making water 124.Because the ice cubes M are separated from the ice-making plate 112 bythe current of the ice-making water 24, double icing which is theconventional problem can be prevented, thus yielding good hemisphericalice cubes M. When all the ice cubes M are removed from both ice-makingplates 112, 112, the temperature of the hot gas rises rapidly and thedeicing thermometer 152 detects the deicing completion temperature(S205). At this time, the controller 144 closes the hot gas valve HV tostop supplying the hot gas to the evaporator 114 (S206) and terminatesthe deicing operation (S207). The controller 144 then starts theice-making operation.

Because the ice cubes M can be removed from the ice-making plate 112promptly this way, it is possible to shorten the deicing time to improvethe daily ice making performance. Because the supply of the deicingwater 130 is stopped before completion of the deicing operation as shownin FIG. 10, the amount of the deicing water 130 to be used can bereduced.

The operation method for the flow-down type ice maker 110 of the fourthembodiment stops supplying the deicing water 130 at the same time assupplying the ice-making water 124 before completion of deicing, asshown in FIG. 10. However, the supply of the deicing water 130 may bestopped when the deicing operation is terminated as the supply of thehot gas is stopped.

Fifth Embodiment

An operation method for an automatic ice maker according to the fifthembodiment will be described next. Because the configuration of theflow-down type ice maker to be used in the fifth embodiment is basicallythe same as the configuration of the fourth embodiment, only differentportions will be described.

At the time of supplying ice-making water 124 upon detection of theice-making water supply temperature by the deicing thermometer 152, thecontroller 144 of the fifth embodiment controls the circulation pump 140so as to intermittently supply the ice-making water 124. When thedeicing thermometer 152 detects the deicing completion temperature, thecontroller 144 controls the circulation pump 140 in such a way as tostop the intermittent supply of the ice-making water 124 andcontinuously supply the ice-making water 124.

The expression “intermittent supply” means that the supply/stop of theice-making water 124 is executed periodically or non-periodically, andincludes intermittent supply of the ice-making water 124 where thesupply/stop of the ice-making water 124 is repeated at a given interval.The ice-making water supply temperature in the fifth embodiment is setlower than the ice-making water supply temperature in the fourthembodiment, e.g., a temperature lower than the deicing completiontemperature by 25° C. to 35° C. or so.

As shown in the flowchart in FIG. 11, when ice making is completed, thecontroller 144 stops the circulation pump 140 to stop supplying theice-making water 124 from the ice-making water spray pipe 134. At thesame time, the hot gas valve HV is opened to stop supplying therefrigerant to the evaporator 114, thereby terminating the ice-makingoperation (S208). Then, the controller 144 opens the water supply valve146 to supply the deicing water 130 to the bottom side 128 of eachice-making plate 112 from the deicing water spray pipe 136. At the sametime, the controller 144 opens the hot gas valve HV to supply the hotgas to the evaporator 114 to start the deicing operation (S209).

As shown in the timing chart in FIG. 12, when the ice-making operationis shifted to the deicing operation, the supply of the refrigerant andthe ice-making water 124 is stopped (OFF), and the supply of the hot gasand the deicing water 130 is started (ON). When the deicing operation isstarted, the frozen surfaces of the ice cubes M frozen on the ice makingsurface 132 start being liquefied by the hot gas and the deicing water130 supplied. This gradually raises the temperature of the hot gas onthe outlet side of the evaporator 114. When a predetermined time elapsessince the start of the deicing operation, the deicing thermometer 152detects the ice-making water supply temperature (S210).

When the deicing thermometer 152 detects the ice-making water supplytemperature, the controller 144 controls the circulation pump 140 insuch a way as to intermittently pump out the ice-making water 124 to theice-making water spray pipe 134, starting the intermittent supply of theice-making water 124 (initiation of the intermittent supply ofice-making water: S211). As shown in FIG. 12, specifically, when theice-making water supply temperature is detected, the controller 144executes a cycle where the supply and stop of the ice-making water 124at a given interval, e.g., the supply of the ice-making water 124 for 5seconds and then the stop of the supply of the ice-making water 124 for5 seconds, are repeated.

The interval between the supply and stop of the ice-making water 124 ispreferably 5 to 10 seconds or so, which is not restrictive. The supplyand stop of the ice-making water 124 should not necessarily be executedat a given interval as per the fifth embodiment. For example, only thetime of supplying the ice-making water 124 may be set longer, or thetime of stopping supplying the ice-making water 124 may be set longer.The supply and stop times for the ice-making water 124 may beautomatically changed according to the temperature detected by thedeicing thermometer 152, so that the intermittent supply of theice-making water 124 is executed according to the progressing state ofdeicing.

The operation method of the fifth embodiment demonstrates operationaladvantages similar to those of the fourth embodiment, and suppressesliquefaction of the ice cubes M by the ice-making water 124 as comparedwith the case of the continuous supply of the fourth embodiment. Thismakes it possible to supply the ice-making water 124 at a relativelyearly stage of the deicing operation. That is, the deicing efficiencybecomes higher than that provided by the continuous supply of theice-making water 124, thus shortening the deicing time and furtherimproving the ice making performance. The intermittent supply of theice-making water 124 in deicing operation mode can reduce the amount ofthe ice-making water 124 scattered in the stocker 118.

The ice-making water supply temperature has only to be set to anadequate value according to the ice making performance of the flow-downtype ice maker 110, the site thereof and the like as per the fourthembodiment. The timing of starting the intermittent supply of theice-making water 124 in deicing operation mode can be changed as needed.When the ice-making water supply temperature is set substantially lowerthan the deicing completion temperature, however, the ice-making wateris supplied with liquefaction between the ice cubes M and the ice-makingplate 112 hardly progressing. Accordingly, the supply amount of theice-making water 124 needed to complete deicing increases. In thisrespect, it is preferable that the ice-making water supply temperaturebe set lower than the deicing completion temperature by 30° C. or so.

When deicing further progresses and all the ice cubes M are separatedfrom the ice-making plate 112, the temperature of the hot gas risesrapidly, and the deicing thermometer 152 detects the deicing completiontemperature (S212). At this time, the controller 144 terminates theintermittent supply of the ice-making water 124 (S213), and switches theoperation to the normal operation of continuously supplying theice-making water 124 to the ice making surface 132. At the same time,the controller 144 closes the hot gas valve HV to stop supplying the hotgas to the evaporator 114. The controller 144 closes the water supplyvalve 146 to stop supplying the deicing water 130 (S214) and terminatesthe deicing operation (S215).

Although the operation method for the flow-down type ice maker 110 ofthe fifth embodiment stops supplying the deicing water 130 when deicingis completed as shown in FIG. 12, the intermittent supply of theice-making water 124 may be started with the supply of the deicing water130 being stopped simultaneously as per the fourth embodiment.

Although the deicing thermometer serves as both the deicing completiondetecting unit and the ice-making-water supply start detecting unit inthe fourth and fifth embodiments, separate temperature sensors or thelike may be used. Further, a timer which starts counting when thedeicing operation is started can be used as the ice-making-water supplystart detecting unit. At this time, the continuous supply orintermittent supply of the ice-making water should be started when theice-making-water supply start time set in the timer (ice-making-watersupply start condition) is reached. In this case, the ice-making-watersupply start time is set shorter than the time needed to completedeicing. A temperature sensor (deicing thermometer) or a timer whichmeasures the deicing completion temperature can be used as the deicingcompletion detecting unit in the case of using the timer.

The configuration of the ice-making unit is not limited to those of theembodiments 4 and 5, but an evaporator may be disposed at the bottomside of a single ice-making plate or the ice-making plate may bedisposed inclined. Further, in a case where a deicing thermometer isused as the deicing completion detecting unit, the target whosetemperature is to be detected by the thermometer is not limited to a hotgas, but the temperature of the ice-making plate itself which changeswhen the deicing operation completes may be detected.

1. An operation method for an automatic ice maker comprising the stepsof: in an ice-making operation, cooling an ice-making unit by supplyinga refrigerant to an evaporator of the ice-making unit and generating icecubes by supplying ice-making water to the ice-making unit via acirculation pump; in a deicing operation, supplying a hot gas to theevaporator and supplying deicing water to the ice-making unit from adeicing water supply unit to remove the ice cubes from the ice-makingunit; and driving the circulation pump to start supplying the ice-makingwater to the ice-making unit when a first set time elapses after atemperature detecting unit has detected the temperature of theevaporator in a deicing operation having reached a predetermined settemperature.
 2. The operation method according to claim 1, whereinsupply of the deicing water from the deicing water supply unit isstopped by driving the circulation pump.
 3. The operation methodaccording to claim 1, wherein supply of the deicing water from thedeicing water supply unit is stopped when a second set time set shorterthan the first set time elapses after a temperature detecting unit hasdetected the temperature of the evaporator having reached thepredetermined set temperature.
 4. An operation method for an automaticice maker comprising the steps of: at a time of performing an ice-makingoperation, supplying ice-making water to top sides of ice-making platesby an ice-making water supply unit and supplying a refrigerant to anevaporator disposed in a zigzagged form between bottom sides of theice-making plates; when an operation shifts to a deicing operation upondetection of generation of ice cubes on the top sides of the ice-makingplates, stopping supplying the ice-making water to the top sides of theice-making plates and the refrigerant to the evaporator, and thereaftersupplying deicing water to the bottom sides of the ice-making plates tothereby promote melt separation of the ice cubes from the ice-makingplates; and causing a controller to control the ice-making water supplyunit in such a way as to supply the ice-making water to the top sides ofthe ice-making plates before terminating the deicing operation so thatice cubes remaining on the top sides of the ice-making plates areremoved by the ice-making water.
 5. The operation method according toclaim 4, wherein the controller controls the ice-making water supplyunit to start supplying the ice-making water when an ice-making-watersupply start detecting unit detects a preset ice-making-water supplystart condition before a deicing completion detecting unit which detectscompletion of the deicing operation detects completion of deicing. 6.The operation method according to claim 4 or 5, wherein in a case ofsupplying the ice-making water to the top sides of the ice-making platesbefore terminating the deicing operation, the controller controls theice-making water supply unit to intermittently supply the ice-makingwater.
 7. The operation method according to claim 4 or 5, wherein whensupply of the ice-making water to the top sides of the ice-making platesis started before terminating the deicing operation, the controllercontrols the deicing water supply unit which supplies the deicing water,thereby stopping supplying the deicing water to the bottom sides of theice-making plates.
 8. The operation method according to claim 6, whereinwhen supply of the ice-making water to the top sides of the ice-makingplates is started before terminating the deicing operation, thecontroller controls the deicing water supply unit which supplies thedeicing water, thereby stopping supplying the deicing water to thebottom sides of the ice-making plates.